如何将以下 SQL 语句转换为实体框架

Question

I have the following SQL statement which group result by ToUserId and FromUserId columns, it considers (ToUserId, FromUserId) and (FromUserId, ToUserId) as the same group. It works fine with SQL Server, but I need to convert it to Entity Framework / Linq:

SELECT
    CASE 
        WHEN [ToUserId] < [FromUserId] 
            THEN [ToUserId] 
            ELSE [FromUserId] 
    END AS lesser,
    CASE 
        WHEN [ToUserId] > [FromUserId] 
            THEN [ToUserId] 
            ELSE [FromUserId] 
    END AS greater,
    MAX([DateCreated]) 
FROM
    Chat
GROUP BY
    CASE 
        WHEN [ToUserId] < [FromUserId] 
            THEN [ToUserId] 
            ELSE [FromUserId] 
    END,
    CASE 
        WHEN [ToUserId] > [FromUserId] 
            THEN [ToUserId] 
            ELSE [FromUserId] 
    END